& @lock is

  IS LOCKS:
 
  Key: =<object>
 
  You pass an is lock only if you are the named object.
 
  Example:
    > @lock mystical highway = =magic bus
  Only the magic bus may travel down the mystical highway.  You 
  cannot travel the highway if you are carrying the bus.
  
  See also: @lock carry, @lock normal.